using System;
using System.Runtime.CompilerServices;
using Silk.NET.OpenGL;

namespace gaemstone.Client;

public static class GLExtensions
{
	public static uint CreateAndCompileShader(this GL GL, ShaderType type, string label, string source)
	{
		var shader = GL.CreateShader(type);
		GL.ObjectLabel(ObjectIdentifier.Shader, shader, (uint)label.Length, label);
		GL.ShaderSource(shader, source);
		GL.CompileShader(shader);
		GL.GetShader(shader, ShaderParameterName.CompileStatus, out var result);
		if (result != (int)GLEnum.True) throw new Exception(
			$"Failed compiling shader \"{label}\" ({shader}):\n{GL.GetShaderInfoLog(shader)}");
		return shader;
	}

	public static uint CreateAndLinkProgram(this GL GL, string label, params uint[] shaders)
	{
		var program = GL.CreateProgram();
		GL.ObjectLabel(ObjectIdentifier.Program, program, (uint)label.Length, label);
		foreach (var shader in shaders) GL.AttachShader(program, shader);
		GL.LinkProgram(program);
		foreach (var shader in shaders) GL.DetachShader(program, shader);
		foreach (var shader in shaders) GL.DeleteShader(shader);
		GL.GetProgram(program, ProgramPropertyARB.LinkStatus, out var result);
		if (result != (int)GLEnum.True) throw new Exception(
			$"Failed linking Program \"{label}\" ({program}):\n{GL.GetProgramInfoLog(program)}");
		return program;
	}

	// These overloads are available because without them, the implicit casting
	// (say from T[] to ReadOnlySpan<T>) causes the generic type resolving to break.
	public static uint CreateBufferFromData<T>(this GL GL, T[] data,
			BufferTargetARB target = BufferTargetARB.ArrayBuffer,
			BufferUsageARB usage   = BufferUsageARB.StaticDraw)
		where T : unmanaged
		=> GL.CreateBufferFromData((ReadOnlySpan<T>)data, target, usage);
	public static uint CreateBufferFromData<T>(this GL GL, ArraySegment<T> data,
			BufferTargetARB target = BufferTargetARB.ArrayBuffer,
			BufferUsageARB usage   = BufferUsageARB.StaticDraw)
		where T : unmanaged
		=> GL.CreateBufferFromData((ReadOnlySpan<T>)data, target, usage);
	public static uint CreateBufferFromData<T>(this GL GL, Span<T> data,
			BufferTargetARB target = BufferTargetARB.ArrayBuffer,
			BufferUsageARB usage   = BufferUsageARB.StaticDraw)
		where T : unmanaged
		=> GL.CreateBufferFromData((ReadOnlySpan<T>)data, target, usage);
	public static uint CreateBufferFromData<T>(this GL GL, ReadOnlySpan<T> data,
			BufferTargetARB target = BufferTargetARB.ArrayBuffer,
			BufferUsageARB usage   = BufferUsageARB.StaticDraw)
		where T : unmanaged
	{
		var buffer = GL.GenBuffer();
		GL.BindBuffer(target, buffer);
		GL.BufferData(target, (nuint)(data.Length * Unsafe.SizeOf<T>()), data, usage);
		return buffer;
	}
}